I can't disagree with any of Bob's reply. I am not an expert in MSA, but I have considerable experience in oven calibration. Some of what I'll say may be redundant. However, for my thought train to work properly, I have to think serially..
Airflow could indirectly be a parameter. Depending on what you are asking the oven to do, however, is the main factor. Most of my experience is with Burn-in chambers. The largest variable is chamber temp uniformity. The calibration method (not MSA) was a chamber profile (normally nine points: eight corners and the center). Depending on the product spec, it was a greater than spec (for a 150 Deg C burnin oven, for example, the critical parameter was to be certain each device was at least as hot as 150 Deg C).
If profiles didn't pass, chamber vents were opened or blocked, and door gaskets were occasionally checked/repaired to improve uniformity. Then there is the obvious calibration of the temp controller.
However, for an MSA, I wonder what the value would be. My limited understanding of MSA and it's applicability is to important product parameters. MSA's are normally used for test instruments that measure product parameters. If the oven temperature over a given time produces a quantifiable product parameter, shouldn't the MSA be on that parameter? If it is a curing process, and there is a variability in how well the product is "cured", I wonder if the MSA should be on that parameter.
Perhaps this is just out of my scope of understanding, but I don't know what quantifiable product parameter would be measured.
The variability in the case of an oven would be for example (math omitted for simplicity):
A product is baked for a given time at a given temperature. The product obtains a given specifiable parameter or quality based on the time/temp combination. If product is removed early or late by a given amount of time, what would be the impact on that specifiable parameter or quality? If the temperature is too high or low by a given amount, what will be the quantitative impact?
I would speculate that within a range of time, there would be no impact. But that outside that range, devices would potentially be damaged. As my experience is with semiconductors, when a chip is burned in, things like moisture are baked out, package plastic materials are cured, adhesives are cured, etc.. There is a pretty wide range of temperatures within which it would still be good. The chamber variability relative to temperature range within which product will still meet spec are the temperatures to be considered (in my opinion). The time early or late within which product meets specs compared with accuracy of timer used in the process is time spec to be considered (in my opinion). How early or late operators remove from chamber compared with when the timer goes off is the operator variable (and possibly some other handling variables). ESD could be a factor in some electronics, environment after removal from chamber could be a variable in some other processes.
Anyway, that's my longwinded "two cents."